This invention relates to closures and more particularly to plugs used to fill openings such as a port in a metal member. This type of plug typically has a lead in dimension smaller than the opening of the port. It then expands to a dimension slightly larger than the opening, thus creating a friction fit when the plug is inserted in the port. The plugs are particularly suited to the protection of ports in metal members during shipping and storage.
A long recognized problem in the use of such plugs is that they are difficult and time consuming to remove when the port is to be used or the metal member is to be placed in service. The prior art shows several efforts that have been made to provide a plug that will be simple, quick and easy to remove from the port.
Applicant is aware of the following U.S. Pat. No.: 117,402 to Gibson, et al; U.S. No. Pat. 492,012 to Hale; U.S. Pat. No. 1,370,170 to Ullman; U.S. Pat. No. 1,651,669 to Carpmael; U.S. Pat. No. 2,048,704 to Kraus; U.S. Pat. No. 2,277,713 to Parker; U.S. Pat. No. 3,104,681 to Gray, Jr.; U.S. Pat. No. 3,148,798 to Brown; U.S. Pat. No. 3,543,801 to Thayer, et al; U.S. Pat. No. 3,574,312 to Miller; U.S. Pat. No. 4,046,168 to Milne; U.S. Pat. No. 4,139,023 to Turley; and, U.S. Pat. No. 5,224,514 to Taylor.